Flying spot scanners are used to convert images on film, documents, etc. to digital image representations (input scanner), and vice versa (output scanner). An input flying spot scanner ideally images one location (one pixel) of the image at a time. However, imperfections in the device generally cause some erroneous contributions to the signal not related to the pixel being imaged, such as flare. Output flying spot scanners suffer similar flare imperfections, in which exposure intended for one pixel unintentionally causes some exposure to other pixels.
A typical input flying spot scanner 10, for scanning a sheet of medium 12 such as film, is shown in FIG. 8. A collimated beam 14 from a laser 15 deflects off a rotating polygonal mirror 16, scanning across a stripe portion of the film. The beam intensity is modulated by the image on the film, and then enters an integrating cavity 18 through an entry slot 19, where the light reflects from the internal walls of the cavity 18 one or more times until it exits the cavity through a port 20 in the end of the integrating cavity 18, and enters an optical detector 22, such as a photodiode or photomultiplier tube that produces an output signal on cable 23. Beam shaping optics including a scanning lens 24 and an f-theta lens 26 focus the beam and linearize the scan velocity along the line. The beam 14 traverses a straight line across the film, and the f-theta lens 26 modifies the motion of the beam so that its position across the film varies linearly with time during each scan line. The film 12 is moved perpendicular to the plane of the drawing, so that the deflected laser beam 14 traverses the film in a series of closely spaced scan lines, i.e. the laser beam 14 traverses an entire film frame in a raster pattern. There are many other flying spot scanner designs in use, including variations on this polygon deflected laser design, and very different designs such as CRT (cathode ray tube) scanners, but flying spot scanners generally traverse the film in a raster pattern, imaging one pixel at a time.